The patients with tumors diffusely seeding the peritoneal cavity have a poor prognosis with conventional treatment. Ovarian cancer is one tumor which presents with advanced disease diffusely involving the peritoneal surface in approximately 70% of the 23,000 women who develop ovarian cancer annually in the United States. The disease free survival in these patients at 5 years is less than 10% with conventional management, which involves initial debulking surgery followed by multi-agent chemotherapy. We have been able to sterilize an ovarian tumor similar to this in a mouse model using intraperitoneal photodynamic therapy, i.e. a photosensitizer which localizes in tumor and can be activated by light to destroy cancer cells. We have been interested in incorporating this strategy into the management of patients with ovarian cancer and have thus initiated this Phase I trial.